15.10.–p Quantum Optics: Physical qubits

An integrated quantum repeater at telecom wavelength with single atoms in optical fiber cavities

Date: 
2016-03-10
Author(s): 

Manuel Uphoff, Manuel Brekenfeld, Gerhard Rempe, Stephan Ritter

Reference: 

Appl. Phys. B 122, 46 (2016)

Quantum repeaters promise to enable quantum networks over global distances by circumventing the exponential decrease in success probability inherent in direct photon transmission. We propose a realistic, functionally integrated quantum-repeater implementation based on single atoms in optical cavities. Entanglement is directly generated between the single-atom quantum memory and a photon at telecom wavelength. The latter is collected with high efficiency and adjustable temporal and spectral properties into a spatially well-defined cavity mode.

Cavity-based quantum networks with single atoms and optical photons

Date: 
2015-12-01
Author(s): 

Andreas Reiserer, Gerhard Rempe

Reference: 

Rev. Mod. Phys. 87, 1379 (2015)

Distributed quantum networks will allow users to perform tasks and to interact in ways which are not possible with present-day technology. Their implementation is a key challenge for quantum science and requires the development of stationary quantum nodes that can send and receive as well as store and process quantum information locally. The nodes are connected by quantum channels for flying information carriers, i.e., photons. These channels serve both to directly exchange quantum information between nodes and to distribute entanglement over the whole network.

Realistic and verifiable coherent control of excitonic states in a light harvesting complex

Date: 
2013-07-19
Author(s): 

Filippo Caruso, Simone Montangero, Mohan Sarovar, Tommaso Calarco, Martin B. Plenio, K. Birgitta Whaley,
Stephan Hoyer

Reference: 

arXiv:1307.4807v1

We explore the feasibility of coherent control of excitonic dynamics in light harvesting complexes despite the open nature of these quantum systems. We establish feasible targets for phase and phase/amplitude control of the electronically excited state populations in the Fenna-Mathews-Olson (FMO) complex and analyze the robustness of this control.

Correlated Photon Emission from Multiatom Rydberg Dark States

Date: 
2012-01-24
Author(s): 

J. D. Pritchard, C. S. Adams, K. Mølmer,

Reference: 

URL: http://link.aps.org/doi/10.1103/PhysRevLett.108.043601
DOI: 10.1103/PhysRevLett.108.043601
PACS: 42.50.Ar, 03.65.Yz, 32.80.Rm, 42.50.Gy

We consider three-level atoms driven by two resonant light fields in a ladder scheme where the upper level is a highly excited Rydberg state.

Two-photon quantum interference from separate nitrogen vacancy centers in diamond

Date: 
2011-10-14
Author(s): 

H. Bernien, L. Childress, L. Robledo, M. Markham, D. Twitchen, R. Hanson

Reference: 

Physical Review Letters 108, 043604 (2012)

We report on the observation of quantum interference of the emission from two separate nitrogen vacancy (NV) centers in diamond. Taking advantage of optically induced spin polarization in combination with polarization filtering, we isolate a single transition within the zero-phonon line of the non-resonantly excited NV centers. The time-resolved two-photon interference contrast of this filtered emission reaches 66%. Furthermore, we observe quantum interference from dissimilar NV centers tuned into resonance through the dc Stark effect.

High-fidelity projective readout of a solid-state spin quantum register

Date: 
2011-09-21
Author(s): 

Lucio Robledo, Lilian Childress, Hannes Bernien, Bas Hensen, Paul F. A. Alkemade, Ronald Hanson

Reference: 

Nature 477, 547-578

Initialization and read-out of coupled quantum systems are essential ingredients for the implementation of quantum algorithms1, 2. Single-shot read-out of the state of a multi-quantum-bit (multi-qubit) register would allow direct investigation of quantum correlations (entanglement), and would give access to further key resources such as quantum error correction and deterministic quantum teleportation1. Although spins in solids are attractive candidates for scalable quantum information processing, their single-shot detection has been achieved only for isolated qubits3, 4, 5, 6.

Spin dynamics in the optical cycle of single nitrogen-vacancy centres in diamond

Date: 
2012-02-21
Author(s): 

L. Robledo, H. Bernien, T. van der Sar, R. Hanson

Reference: 

New Journal of Physics13, 025013

We investigate spin-dependent decay and intersystem crossing (ISC) in the optical cycle of single negatively charged nitrogen-vacancy (NV) centres in diamond. We use spin control and pulsed optical excitation to extract both the spin-resolved lifetimes of the excited states and the degree of optically induced spin polarization. By optically exciting the centre with a series of picosecond pulses, we determine the spin-flip probabilities per optical cycle, as well as the spin-dependent probability for ISC.

Rydberg excitation of trapped cold ions: a detailed case study

Date: 
2011-07-29
Author(s): 

F. Schmidt-Kaler, T. Feldker, D. Kolbe, J. Walz, M. Müller, P. Zoller, W. Li, I. Lesanovsky

Reference: 

New Journal of Physics 13, 075014 (2011)
doi:10.1088/1367-2630/13/7/075014

We present a detailed theoretical and conceptual study of a planned experiment to excite Rydberg states of ions trapped in a Paul trap. The ultimate goal is to exploit the strong state-dependent interactions between Rydberg ions to implement quantum information processing protocols and simulate the dynamics of strongly interacting spin systems. We highlight the promise of this approach when combining the high degree of control and readout of quantum states in trapped ion crystals with the novel and fast gate schemes based on interacting giant Rydberg atomic dipole moments.

Interaction of a Laser with a Qubit in Thermal Motion and its Application to Robust and Efficient Readout

Date: 
2011-09-16
Author(s): 

U. G. Poschinger, A. Walther, M. Hettrich, F. Ziesel, F. Schmidt-Kaler

Reference: 

arXiv:1109.3643 (2011)

We present a detailed theoretical and experimental study on the optical control of a trapped-ion qubit subject to thermally induced fluctuations of the Rabi frequency. The coupling fluctuations are caused by thermal excitation on three harmonic oscillator modes. We develop an effective Maxwell-Boltzmann theory which leads to a replacement of several quantized oscillator modes by an effective continuous probability distribution function for the Rabi frequency. The model is experimentally verified for driving the quadrupole transition with resonant square pulses.

Correlated photon emission from multi--atom Rydberg dark states

Date: 
2011-08-25
Author(s): 

J. D. Pritchard, C. S. Adams, K. Mølmer

Reference: 

arXiv:1108.5165

We consider three level atoms driven by two resonant light fields in a ladder scheme where the upper level is a highly excited Rydberg state. We show that the dipole--dipole interactions between Rydberg excited atoms prevents the formation of single particle dark states and leads to strongly correlated photon emission from atoms separated by distances large compared to the emission wavelength. For two atoms, correlated photon pairs are emitted with an angular distribution given by a coherent sum of the independent dipolar fields.

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